Limitations on resident work hours, the involvement of communication issues in a significant number of adverse events, and regulatory pressure from The Joint Commission to standardize handoff practices together contribute to a need to understand and improve patient handoffs in hospitals. Efforts to standardize such transitions, however, may be limited without a better understanding of the influence that social factors and organizational structures exert on transfers of information, control and responsibility for patients or of the variation in handoff practice that is necessary in order to ensure continuity of care. Lacking such an understanding, efforts to improve handoffs run the risk of inadvertently introducing new challenges to safety and quality of care. Furthermore, while research on patient handoff practices is growing, little attention has been directed toward a crucial form of handoff that occurs when patients are admitted from the emergency department (ED) of a hospital to an inpatient service. To begin addressing these deficiencies, this dissertation research will follow a grounded theory methodology, involving semi-structured interviews and ethnography to examine admission handoffs between physicians in the ED and various inpatient services of a large U.S. tertiary teaching hospital. The aim of the study is to develop a conceptual framework of the sources and nature of variety in admission handoff practice to highlight the importance of complex situational factors that affect handoff communication and interaction. This framework will contribute to handoff practice improvement by providing a better understanding of the unique complexities of coordinating care across organizational and specialization boundaries;evidence of the role that variations in patients, physicians, and larger social and organizational factors play in shaping care transitions;insight into the functions of handoffs beyond the conveying of patient information;and a guide for identifying fruitful targets for improvement, as well as, important sources of variation that may need to be protected.